1. Field of the Invention
The present invention relates to anti-extruding sealing means or packers for testing under fluid pressure a segment of pipe or the connection between a segment of pipe and a coupling. More particularly, the present invention relates to elastomer packers which in one application are employed inside a pipe to seal off a particular section of the pipe by using two of such devices spaced apart and filling the annular space created between them with a liquid or gas under high pressure in order to check the strength of the pipes outer wall or the coupling. Fluid is then injected into the packers so that they inflate and come into contact with the inside wall of the pipe so as to contain the test fluid on either side of the seal and thus test the integrity of pipe or the connection between the threads on the pipe and the threads of the coupling.
2. General Background
In the oil and gas production industry conduits or tubing sections of threaded pipe are joined end to end i.e. pin end to box end, to convey fluids. It is desirable that the joints be strong and that a tight fit exist and that the body wall be strong enough to withstand relatively high internal pressures. It is common practice in the industry to plug off the ends of each particular joint by screwing test plugs onto the respective threaded ends and to fill the inside of the pipe with a fluid under high pressure to check for leaks behind the collar. Evidence of any leaks when pressured up to standardized test pressure is an indication that either the external threads on the pin end or the internal threads on the coupling were improperly machined and thus not mating properly, or that they may not have been screwed together with adequate torque, or that the body wall is of insufficient strength to withstand the pressure. This test procedure is followed to simulate "down hole" conditions when there is pressure exerted on the connection.
This procedure was very inefficient due to the need to fill up the entire inside of the full length of the tubing with fluid until the introduction of the "Hydro Pressure Thread Tester" disclosed in U.S. Pat. No. 4,733,554, issued to Richard Lazes, by requiring only small volume high pressure pumps and only small quantities of test fluid. However, even after Lazes '554, one further problem which remained after inflation of the packer was its tendency to extrude or migrate along the pipe in the direction of flow of the test fluid introduced through the orifice in the mandrel thus causing it to become stuck in the pipe and damage seals.
The apparatus of the present invention provides anti-extrusion segments or rings mounted on the packer which expand when the packer is inflated and are there by forced into contact with the pipe being tested to prevent extrusion therealong. These anti-extrusion segments or ring sections will also work on conventional packers when the geometry of the packers permit adequate seal material to be present beneath the anti-extrusion means. With the apparatus of the present invention the ring sections expand and bind against the inside diameter of the pipe so that the packer does not extrude or migrate down the pipe in the direction of the flow of the test fluid.